Enhanced energy storage and luminescence properties of Bi_0.5Na_0.5TiO₃ based lead-free relaxor ceramics by rare earth ions

The scarcity of chemical energy resources makes it urgent to develop electronic devices for energy efficient storage and utilization. In recent years, lead-free dielectric capacitors have attracted great attention because of their advantages such as high charging and discharging rates, high power density and eco-friendliness. In this work, we enhanced the energy storage and photoluminescence properties of the 0.6Bi_0.5Na_0.5TiO₃-0.4BaZr_0.3Ti_0.7O₃ system by introducing the rare earth ion Er³⁺ (BNT-BZT: x%Er³⁺). The results suggest that the recoverable energy storage density of 1.87 J/cm³ and energy storage efficiency of 80.6 % are achieved for BNT-BZT: x%Er³⁺ ceramics under 170 kV/cm. For x = 0.4, the highest energy storage efficiency of 87.4 % is achieved. Within the temperature range of 30–150 °C, all ceramics exhibit less than 10 % degradation in energy storage performance, thereby demonstrating exceptional temperature stability. Meanwhile, BNT-BZT:0.2 %Er³⁺ ceramics maintain a relatively stable energy storage behavior at different frequencies (1–100 Hz), and with the increase of frequency, W_rec and η decrease by 10.3 % and 8 %, respectively. Herein, an increase in the concentration of Er³⁺ doping resulted in a substantial enhancement of luminescence intensity, recording a significant 95.48 % increase under light excitation at 487 nm. This study provides a new method for the design of rare-earth modified dielectric capacitor materials, which is also important for practical applications.